Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.53	7.674%	$111.4749	$111.47	$111.45	$111.50
Purchase #2	$157.86	13.607%	$179.34	$179.34	$179.35	$179.30
Purchase #3	$223.28	13.866%	$254.24	$254.24	$254.25	$254.20
Purchase #4	$214.26	10.551%	$236.8666	$236.87	$236.85	$236.90
Purchase #5	$70.63	10.666%	$78.1634	$78.16	$78.15	$78.20
Purchase #6	$125.92	8.839%	$137.0501	$137.05	$137.05	$137.10
Purchase #7	$192.72	11.841%	$215.54	$215.54	$215.55	$215.50
7 purchase totals =	$1,088.20		$1,212.6750	$1,212.67	$1,212.65	$1,212.70